INFLUENCE OF AGING ON T-CELL SUB-POPULATIONS INVOLVED IN THE INVITRO GENERATION OF ALLOGENEIC CYTOTOXICITY

Cell-mediated lympholysis (CML) generated in allogeneic mixed lymphocyte culture from young or old responding spleen cells was studied. CML from old responding cells was constantly inferior to that of young spleen cells when infraoptimal conditions of allogeneic sensitization were achieved by lowering the number of allogeneic stimulating cells. Studies on the CML obtained from mixtures of irradiated old spleen cells with young responding cells (and reciprocally) showed that old spleens were lacking a helpercell subpopulation sensitive to 2000 rad irradiation but resistant to 400 rad. Conversely, another subpopulation of helper cells, resistant to 2000 rad remained unaffected by aging. With optimal conditions of allogeneic sensitization, produced by increasing the number of stimulating cells, a small but significant decrease of the CML from old spleen cells was still observed. Under such conditions of sensitization some experiments in which old and young unirradiated responding cells were combined showed a suppressive effect by the old mouse spleen cells on the CML of young spieen cells, and suggested a possible increase of suppressor T cells with age. Thus, the CML decrease in aged mice appears to be due to the simultaneous alteration of different T-cell subsets. © 1979.